Optical fiber for communication purposes is well known. Optical fiber is commonly wound in a coil or skein which can be rapidly paid out, for example, behind a missile which is controlled by signals conducted by the fiber from a remote controller to adjust the flight path of the missile.
The state of the art payout system for optical fiber guided missile systems employs precision helically wound, center fed skeins of fiber. This reel-less configuration is mechanically simple, with no rotating inertial mass, which could lead to fiber breakage during missile deployment due to tensile stress. However, a major weakness of this construction is its intrinsic lack of mechanical integrity and tendency to spontaneously unravel. Hence this "twine ball" payout approach requires a containment system which can be adjusted to withstand a wide range of conditions during use. For example, it must maintain the necessary precision wound construction during the vibration "g" loading and under environmental extremes expected during a mission such as extremes of temperature and humidity, yet be not so rigidly constrained as to cause undue tensile stress on the fiber during payout.
Organic low tack adhesives are known for this purpose. The prior art has involved impregnating wound skeins with such low tack materials. The problem with this technique is the difficulty of achieving impregnation uniformity throughout the multiple layers of the skein. U.S. Pat. No. 4,950,049 to Darsey et al. addresses this problem by first pre-coating the fiber strand with a uniform layer of adhesive, and then winding. The adhesive is a thermally activated organic adhesive. The process sequence first applies the adhesive to the fiber in a zero tack state, then precision winding, and then thermally activating the adhesive system to tackiness. This achieves a bound precision wound skein, free of the microbending and built-in stresses inevitable in directly winding sticky fiber. However, with this approach, aging degradation and tackiness drift with temperature and humidity are still major problems upsetting the fine tuning required for reliable payout. Moreover, by their very nature, low tack adhesives are also likely to be low modulus materials with a thickness on the order of the fiber diameter (about 125 microns) so that, during storage, the twined fibers have a tendency to take a deformation set at bearing contact points, farther disrupting skein payout evenness.
Winding processes are also well known for such prior art arrangements. Thus, U.S. Pat. No. 5,179,613 to Cronk describes a typical process for forming a self-supporting coil of optical fiber which has convolutions adhered together by a thermoplastic adhesive.